1. Field of the Invention
The present invention relates to a photographic light-sensitive sheet for the color diffusion transfer process and, more particularly, to a silver halide photographic light-sensitive sheet for the color diffusion transfer process containing a novel dye releasing redox (DDR) compound.
2. Description of the Prior Art
Color diffusion transfer color image forming processes using a dye releasing redox compound are described in Japanese Patent Application (OPI) Nos. 33826/73 (The term "OPI" as used herein refers to a "published unexamined Japanese patent application"), 114424/74, 126331/74, 126332/74, 115528/75 and 104343/76, U.S. Pat. Nos. 3,928,312, 3,931,144 and 3,954,476 and Research Disclosure, No. 13024 (1975), ibid., No. 16475 (1977). The term "dye releasing redox compound" means a compound containing therein a redox moiety and a dye moiety (including a precursor thereof). The redox moiety renders the redox compound immobile due to a ballast group attached thereto, but upon redox reaction under alkaline conditions the comound per se splits and releases a compound having the dye moiety (a dye compound). That is, when a light-sensitive element having a light-sensitive silver halide emulsion layer and a dye-releasing redox compound associated therewith is exposed and developed with an alkaline processing solution, the redox compound per se is oxidized in proportion to the amount of developed silver halide and the compound splits into a compound containing the dye moiety and a nondiffusible compound in the alkaline processing solution. As a result, the compound containing the dye moiety diffuses into an image-receiving layer to provide a transferred image therein.
Examples of dye-releasing redox compounds which release magenta dyes are described in Japanese Patent Application (OPI) Nos. 115528/75 and 114424/74, U.S. Pat. Nos. 3,932,380 and 3,931,144, etc. However, technical problems are encountered using these magenta dye releasing redox compounds specifically described in such prior art in that the transferred images have insufficient stability. For example, the light fastness of the images is not adequate and the images fade to a large extent even in a dark place. Also, the transfer of the dye compound is not adequate.
For instance, with respect to the fading-in-dark of transferred dye images, it has been known that unreacted monomer (such as acrylic acid, butyl acrylate, etc.) in the neutralizing layer containing a polymer acid such as polyacrylic acid, a copolymer of acrylic acid and butyl acrylate, etc., as disclosed in U.S. Pat. No. 3,362,819 hereinafter described, adversely influences the fading-in-dark of transferred dye images. It has also been found upon further investigation that unreacted butyl acrylate monomer exceptionally degrades the fading-in-dark of magenta dye images obtained from prior art dye-releasing redox compounds such as described in U.S. Pat. No. 3,932,380. However, it is extremely difficult from a technical standpoint to limit the amount of unreacted monomer during the synthesis of polymer acid for a neutralizing layer to an extent that does not adversely influence thelight fastness of the images. Therefore, it has been desired to develop a redox compound which releases a dye compound which is less susceptible to such a monomer.